The present invention relates to an ink jet head, and to a method for the manufacture thereof. More specifically, the present invention relates to an ink jet head comprising a nozzle member on which surface a thin film having water repellency has been formed, and to a method for the manufacture of such an ink jet head.
With the recent improvement in operation speed and image quality, and the reduction in production cost of recording devices such as a printer, a word-processing machine, a facsimile machine, or the like, many of the recording devices employ an ink jet recording method. Typically, the ink jet head employed in such an ink jet recording device has nozzles from which ink droplets are jetted toward a recording medium such as a sheet of paper on which these ink droplets land to effect printing.
Incidentally, if water repellency at a portion surrounding a nozzle orifice of the nozzle member is insufficient, this will cause the ink to readily adhere to the surrounding portion. If ink adheres to a portion surrounding a nozzle orifice, this will reduce the linearity in travel direction of ink droplets jetted from that nozzle orifice. It is therefore difficult to effect satisfactory printing. To cope with such a problem, a water repellent film is usually formed on the surface of a nozzle member, as disclosed in, for example, Japanese Unexamined Patent Gazette No. H06-87216.
Water repellent films which are formed on the surface of nozzle members are roughly divided, by formation method, into two types, namely water repellent films of the application type and plasma polymerization films. The application-type water repellent film is a film formed by application of a water repellent material on the surface of a nozzle member by dipping, spray-coating, or spin-coating. On the other hand, the plasma polymerization film is a film formed by plasma polymerization.
Generally, in a typical ink jet head, cleaning including wiping of ink adhered to the surface of a nozzle member is carried out at regular intervals. However, although the film thickness of conventional water repellent films of the application type is not thin at all, these water repellent films readily come to peel off and are poor in abrasion resistance. In other words, wiping causes such a conventional water repellent film to readily peel off and wear out. For this reason, it is difficult to maintain water repellency over a long period. Accordingly, in order to improve abrasion resistance, the film thickness may be increased to a further extent. However, if the film thickness is too thick, this will result in distortion in film shape when nozzle orifices are formed and sagging in the vicinity of the nozzle orifices. Due to such drawbacks, the state of jetting ink droplets is likely to become unstable.
Conversely, the film thickness formable by plasma polymerization is just 10 nm at most, so that plasma polymerization films are likely to be poor in abrasion resistance because of their thinness. Moreover, since the degree of adhesion between the film and the base material (i.e., the nozzle member) is generally poor, it is required to provide an adhesive layer, such as an inorganic film, between them in order to improve the degree of adhesion. Furthermore, the plasma polymerization requires the provision of vacuum equipment. Moreover, the plasma polymerization requires a greater number of process steps for the formation of water repellent films. As a result, the cost of equipment increases considerably.
Bearing in mind the above-described points, the present invention was made. Accordingly, an object of the present invention is to provide an ink jet head in which a water repellent thin film, which is less readily peelable, superior in abrasion resistance, and capable of easily making the state of jetting ink droplets stable, is formed and to provide a method for the manufacture thereof.
In order to achieve the object, the present invention provides an ink jet head. The ink jet head of the present invention comprises a nozzle member on which surface a water repellent thin film, containing therein a molecule in which fluoroalkyl chains are bonded to or dispersed in silicon oxide, has been formed.
As a result of such arrangement, the silicon oxide enhances abrasion resistance, while the fluoroalkyl chain imparts water repellency, whereby an ink jet head having a water repellent thin film superior in abrasion resistance and having a long life span can be achieved.
It is preferred that the water repellent thin film is formed, having a thickness of from 10 nm to 1000 nm.
Water repellent thin films are likely to peel off and undergo a drop in abrasion resistance if their film thickness is too thin. On the other hand, if the film thickness is too thick, then there occurs distortion in film shape and cracking is likely to occur. If it is arranged such that the film thickness is from 10 nm to 1000 nm, this makes it possible to form a water repellent thin film which is uniform in film shape, superior in abrasion resistance, and capable of jetting ink droplets in a stable manner. Further, being thin in film thickness, the water repellent thin film of the present invention facilitates the miniaturization of nozzles. Moreover, because of its thinness, the water repellent thin film of the present invention comes to derive a high heat conductivity, therefore being unsusceptible to ill effects such as thin film damage and peeling-off at the time when nozzle orifices are formed by laser beam machining or electrical discharge machining. Moreover, being superior in adhesion, even when nozzle orifice formation is carried out using mechanical machining such as punching machining, the water repellent thin film of the present invention will not peel off at the time of such machining. This therefore allows mechanical machining to easily form nozzle orifices.
It is preferred that the water repellent thin film is formed such that the density of the fluoroalkyl chain-containing molecule at the side of an upper surface of the water repellent thin film is thicker than that at the side of an interface between the water repellent thin film and the nozzle member.
Generally, molecules which impart water repellency exhibit poor adhesion for the nozzle member (i.e., the base material). However, as a result of the above-described arrangement, the fluoroalkyl chain-containing molecule is less dense at the interface between the water repellent thin film and the nozzle member, thereby providing a satisfactory degree of adhesion between the water repellent thin film and the nozzle member. On the other hand, at the side of the upper surface of the water repellent thin film the density of the fluoroalkyl chain-containing molecule thickens, thereby increasing the water repellency.
The present invention provides a method of manufacturing an ink jet head. More specifically, the present invention discloses a method of manufacturing an ink jet head having a nozzle member on which surface a water repellent thin film has been formed, the method comprising the steps of (a) applying, onto a surface of the nozzle member, a coat liquid in which a methoxysilane or ethoxysilane compound which is a precursor of silicon oxide and an ethoxysilane or methoxysilane compound containing therein a carbon fluoride chain are dissolved and (b) thereafter, drying the nozzle member.
By a process of xe2x80x9cdryingxe2x80x9d used here may be meant only one of dehydration and thermal baking or both of them.
Because of such arrangement, it is possible to form a water repellent film, only by applying the coat liquid onto the surface of the nozzle member in an atmosphere at room temperature. This therefore provides a method of manufacturing an ink jet head which requires a less number of process steps and which is inexpensive in production cost. Moreover, unlike the plasma polymerization thin film formation, there is no need to place a nozzle member in the vacuum furnace when forming a water repellent thin film. This facilitates producing thin films with a larger area.
The present invention provides another method of manufacturing an ink jet head. More specifically, the present invention discloses a method of manufacturing an ink jet head having a nozzle member on which surface a water repellent thin film has been formed, the method comprising the steps of (a) applying, onto a surface of the nozzle member, a first coat liquid in which a methoxysilane or ethoxysilane compound which is a precursor of silicon oxide is dissolved, (b) applying, onto the nozzle member surface coated with said first coat liquid, a second coat liquid in which a methoxysilane or ethoxysilane compound which is a precursor of silicon oxide and an ethoxysilane or methoxysilane compound which contains therein a carbon fluoride chain are dissolved, and (c) thereafter, drying the nozzle member.
Accordingly, the first coat liquid includes neither a carbon fluoride chain-containing ethoxysilane compound nor a carbon fluoride chain-containing methoxysilane compound. This means that the water repellent thin film contains, at its portion in the vicinity of an interface with the nozzle member, little water repellent molecule, therefore enhancing the degree of adhesion between the water repellent thin film and the nozzle member.
The present invention provides still another method of manufacturing an ink jet head. More specifically, the present invention discloses a method of manufacturing an ink jet head having a nozzle member on which surface a water repellent thin film has been formed; the method comprising the steps of (a) applying, onto a surface of the nozzle member, a coat liquid in which a methoxysilane or ethoxysilane compound which is a precursor of silicon oxide and an ethoxysilane or methoxysilane compound containing therein a carbon fluoride chain are dissolved, (b) thereafter, drying the nozzle member, and (c) thereafter, forming a nozzle orifice in the nozzle member.
As described above, since the formation of the orifice nozzle is preceded by that of the water repellent thin film, this ensures that the nozzle orifice is prevented from becoming clogged by the water repellent thin film, unlike the case in which the water repellent thin film is formed after the nozzle orifice formation.
The present invention provides another method of manufacturing an ink jet head. More specifically, the present invention discloses a method of manufacturing an ink jet head having a nozzle member on which surface a water repellent thin film has been formed, the method comprising the steps of (a) applying, onto a surface of the nozzle member, a first coat liquid in which a methoxysilane or ethoxysilane compound which is a precursor of silicon oxide is dissolved, (b) applying, onto the nozzle member surface coated with the first coat liquid, a second coat liquid in which a methoxysilane or ethoxysilane compound which is a precursor of silicon oxide and an ethoxysilane or methoxysilane compound which contains therein a carbon fluoride chain are dissolved, (c) thereafter, drying said nozzle member, and (d) thereafter, forming a nozzle orifice in the nozzle member.
As a result of such arrangement, the water repellent thin film contains, at its portion in the vicinity of an interface with the nozzle member, little water repellent molecule, therefore enhancing the degree of adhesion between the water repellent thin film and the nozzle member. Moreover, it is ensured that the nozzle orifice is prevented from becoming clogged by the water repellent thin film.
It is especially preferred that the nozzle orifice forming step, which is carried out after the water repellent thin film formation step, is a step of forming nozzle orifices by electrical discharge machining.
The use of an electrical discharge machining technique makes it possible to provide a wide-range setting of the taper angle of nozzle orifices. In addition, heat produced by electrical discharge machining causes water-repellency molecules contained in side-wall portions of the water-repellency thin film to vapor, wherein the inside of the nozzles becomes hydrophilic. This stabilizes the jetting of ink droplets.
As described above, in accordance with the present invention, it is possible to achieve an ink jet head in which a water repellent thin film, which is less readily peelable, superior in abrasion resistance, and capable of easily making the state of jetting ink droplets stable, has been formed.
The first arrangement, in which the water repellent thin film has a film thickness of from 10 nm to 1000 nm, facilitates the formation of uniform thin films having a neat film shape, therefore facilitating the miniaturization of nozzles.
The second arrangement, in which the molecule having a fluoroalkyl chain in the water repellent thin film is more dense at the side of the upper surface (i.e., right surface) of the water repellent thin film than at the side of the interface between the water repellent thin film and the nozzle member, not only enhances the degree of adhesion between the water repellent thin film and the nozzle member, but also improves water repellency at the surface.
The third arrangement, in which nozzle orifice formation is carried out by electrical discharge machining, makes it possible to provide a wide-range setting of the taper angle of nozzle orifices. Moreover, after the water repellent thin film is formed, the nozzle orifice is formed by means of electrical discharge machining. This causes water repellent molecules to vapor from side-wall portions on the nozzle orifice side of the water repellent thin film, whereby the jetting of ink droplets can be stabilized.